This project will investigate the associated structure of heart adenylyl cyclase (Acy) and changes in this structure as a function of its interaction with hormones or drugs. We will evaluate the relative spatial relations of the hormone binding sites with respect to one another, the size and shape of the binding proteins, and the characteristics of the association with the enzymatic subunit. The project is divided into two parts: a) further purification of the Acy complex and dissociation of the complex into its subunits; b) utilization of specific fluorescent probes which are hybrids of the cyclase substrates: hormonal, nucleotide, lipid, and drug derivatives to probe environment, conformation and spatial aspects of the Acy complex. We will use resonance energy transfer of excitation to ascertain the separation distances between sites of interaction. After acquiring information as to the structure of the Acy, we will extend our studies to a comparison of the cyclase structure in diseased heart and other tissues.